/Engine/Source/Runtime/Engine/Classes/Kismet/KismetMathLibrary.h
Uses a simple spring model to interpolate a quaternion from Current to Target.
static FQuat QuaternionSpringInterp ( FQuat Current, FQuat Target, [FQuaternionSpringState](API\Runtime\Engine\Kismet\FQuaternionSpringState) & SpringState, float Stiffness, float CriticalDampingFactor, float DeltaTime, float Mass, float TargetVelocityAmount, bool bInitializeFromTarget )